This invention relates generally to a punched tape system for controlling the operation of a machine. Basically, punched tape control systems operate through the use of a closed loop punched or perforated tape which contains appropriately spaced perforations to convey information to control the various operations of the machine.
Punched tape of the type utilized to control the operation of machines typically has a plurality of parallel tracks or channels. One of these tracks or channels contains a plurality of sprocket holes which are engaged by a drive sprocket. The rotation of the drive sprocket sequentially engages the sprocket holes to advance the tape through a tape reading station. The tape contains perforations in the various channels to convey information which is sensed or read by the tape reader and the particular location of these data holes is converted by suitable circuitry to control the operation of the machine.
One problem with the prior systems is that the sprocket holes do not convey any information. This reduces the number of available channels or tracks on the tape.
A second problem can be best understood by considering the type of information contained on the tape. If it is desired to have the machine advance stock material, under the prior systems it was often necessary to place a perforation in a particular track (or a series of perforations in a straight line transverse to the longitudinal axis of the tape) to start the advancing operation. Then, when it was desired to terminate the advancing operation another perforation or series of perforations in a different track was necessary.
The alternate way of accomplishing the same result, according to the prior art, was to provide a sequence or series of perforations in a particular track to indicate the continuation of a given machine operation. Thus a series of five consecutive perforations in a particular track or channel were utilized to indicate that the feeding operation was to continue for the length of time it took the tape to be advanced by the drive sprocket the equivalent of five sprocket holes.
None of the prior art systems for punched tape machine controls therefore, made optimum use of the available space on the tape. None of the prior art systems made optimum use of the sprocket holes.